Extraction of a rivet requires removal of at least the flange portion of a rivet head at one side of the riveted construction to enable ejection of the rivet at the other side of the construction. Removal of the rivet head with a grinding tool or with a general purpose drill can easily result in damaging of the structural members that are secured together by the rivet. It is difficult to position and control such tools in a manner which will accomplish the desired result without grinding or cutting into the structural members. Such damage may be unacceptable in instances where new rivets will be installed to enable reuse of the riveted structure.
An ordinary drill can also be ineffective for rivet removal in instances where the rivet is loose and simply rotates with the drill.
Prior U.S. Pat. No. 3,620,635, issued Nov. 16, 1971 to Bert L. DalBianco and which is entitled "Rivet Removing Tool", discloses a tool which is specifically designed for rivet removal. One end of a tubular casing of the tool is provided with teeth and is shaped to fit onto the rivet head in a centered relationship. Rotation of the rivet is prevented by exerting pressure on the rivet head with the casing. A rotatable drill bit within the casing may be traveled towards the casing. The bit has teeth of specialized configuration which make a circular cut that separates the peripheral portion of the rivet head from the central portion thereby enabling removal of the remainder of the rivet.
Prior rivet removers of the above discussed kind are proportioned for use with rivets of a particular size or limited range of sizes. Thus a number of such tools of different sizes are needed for optimum performance in extracting rivets of widely varying size. It would be advantageous if a single such tool was adaptable to rivets of diverse different sizes.
Avoiding damage to the riveted structural members during use of the prior rivet removers is dependent on operator skill. It would also be advantageous if the tool itself limited penetration into the rivet head and did so in a manner that is compatible with rivets of varying sizes.
The above discussed prior rivet remover uses a drill bit of specialized configuration which, as noted above, is designed for use on rivets of a particular size or size range. If an ordinary twist drill bit were to be used in the prior rivet removers, the spiral grooves on such a bit would act to draw rivet shavings up into the casing of the tool and the accumulation of such material could adversely affect the operation of the device.
The present invention is directed to overcoming one or more of the problems discussed above.